Do fungus gnats damage roots?
Dave
8 years ago
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gardengal48 (PNW Z8/9)
8 years agoewwmayo
8 years agoRelated Discussions
Do i have fungus gnats???
Comments (3)Edymnion is incorrect in his/her explanation of fungus gnats. In our homes and greenhouses, they are not necessarily fungus feeders though their populations certainly explode under the moist conditions that mold/fungi thrive in. They feed upon decomposed or decomposing organic matter, such as the stuff that (most) of our potting mediums are comprised of, algae, fungi (if there is any in your potting mix (not in mine!!), and plant roots. Ohiofem explained it perfectly...a few of these little insects are not something to worry about. But they (the tiny, maggoty larvae) will begin to feed on tender plant roots as their populations rise. That's why we worry about it when our seedling trays become infested. Many germination mediums and even common potting mixes are very fine textured and peaty...a perfect (though artificial) environment for fungus gnats, even it you don't keep it too moist all of the time. Inside, where there is no place else for the adults to lay eggs, our containerized plants can soon become over-run with the larvae. At this time of year, you can find mosquito dunks at most garden centers and even hardware stores. Break a few pieces from a dunk and let it soak in your full watering bucket over night. Use that water for your plants. For the next several watering cycles, use the 'dunk' water only. Mosquito dunks contain a naturally occurring bacterium that affects the larvae of certain insects, such as mosquitoes, black flies (of the northeast), some shore flies, and fungus gnats. The larvae feed on the dunks and the ingested bacterium infects them. This bacterium, named Bacillus thuringiensis-israelensis (Bt-i) is harmless to anything but the targeted larvae. Next time, search for a much coarser potting mix, one that cannot support fungus gnat larvae. Such a medium can still be used as a germination mix by using a shallow layer of the peaty stuff on top of the coarser material. Also, as has been said, moisture levels need to be monitored carefully. These insects really love very moist medium. My potting soil, for example, contains more pine bark than peat moss. I haven't seen a fungus gnat in many, many years....See MoreFungus gnats!
Comments (17)Pop cans may or may not cause water to perch higher in containers, depending on how the soil is situated relative to the pop cans. If you used something as a barrier, like screen/cloth/paper, it's probable that it DID raise the location of the PWT. Josh was exactly right when he said that perlite won't do much to change the ht of the PWT and it won't much affect the flow through rates. What it DOES do is reduce water retention, but that is not enough. It's the perched water that kills. The water in the layer of soggy soil at the bottom of most containers when using soils with significant fractions of peat, compost, coir, topsoil, sand, or any other very fine particulates. The height of the PWT is directly related to particle size, and no matter how much growers using these soils want you to believe otherwise, they ARE dealing with the effects of PWTs and their trappings - over-watering and/or accumulating salts. In order to be free of the negative effects of perched water, you need to have a soil that has a very large % of its volume comprised of particles >1/10 - 1/8". You cannot be rid of the effects of perched water by amending peat/coir/compost/sand/topsoil-based soils. As an illustration: If you start with a quart of pudding, how much perlite do you need to add to get it to drain properly and hold some air? Even 60% perlite isn't going to do it. Only when you start to approach the perlite fraction of 80%+ do you start to see a little better drainage and SOME aeration. If you mix pine bark & peat 50-50, you get a soil with the drainage (flow through rates) and aeration of peat. FWIW - gnats don't dislike fresh circulating air. They live by the billions outdoors in their natural habitat. Indoors is actually foreign and unfamiliar territory for them. They simply love wet soils with a high organic fraction that breaks down easily, and organic fertilizers like various meals and fish emulsion MUST be an aphrodisiac because they multiply like crazzzy with the combination of wet soil/organic fertilizer. A little about container size from one of my other posts: How large a container "can" or "should" be, depends on the relationship between the mass of the plant material you are working with and your choice of soil. We often concern ourselves with "over-potting" (using a container that is too large), but "over-potting" is a term that arises from a lack of a basic understanding about the relationship we will look at, which logically determines appropriate container size. It's often parroted that you should only move up one container size when "potting-up". The reasoning is, that when potting up to a container more than one size larger, the soil will remain wet too long and cause root rot issues, but it is the size/mass of the plant material you are working with, and the physical properties of the soil you choose that determines both the upper & lower limits of appropriate container size - not a formulaic upward progression of container sizes. In many cases, after root pruning a plant, it may even be appropriate to step down a container size or two, but as you will see, that also depends on the physical properties of the soil you choose. Plants grown in 'slow' (slow-draining/water-retentive) soils need to be grown in containers with smaller soil volumes so that the plant can use water quickly, allowing air to return to the soil before root issues beyond impaired root function/metabolism become a limiting factor. We know that the anaerobic (airless) conditions that accompany soggy soils quickly kill fine roots and impair root function/metabolism. We also know smaller soil volumes and the root constriction that accompany them cause plants to both extend branches and gain o/a mass much more slowly - a bane if rapid growth is the goal - a boon if growth restriction and a compact plant are what you have your sights set on. Conversely, rampant growth can be had by growing in very large containers and in very fast soils where frequent watering and fertilizing is required - so it's not that plants rebel at being potted into very large containers per se, but rather, they rebel at being potted into very large containers with a soil that is too slow and water-retentive. This is a key point. We know that there is an inverse relationship between soil particle size and the height of the perched water table (PWT) in containers. As particle size increases, the height of the PWT decreases, until at about a particle size of just under 1/8 inch, soils will no longer hold perched water. If there is no perched water, the soil is ALWAYS well aerated, even when the soil is at container capacity (fully saturated). So, if you aim for a soil (like the gritty mix) composed primarily of particles larger than 1/16", there is no upper limit to container size, other than what you can practically manage. The lower size limit will be determined by the soil volume's ability to allow room for roots to 'run' and to furnish water enough to sustain the plant between irrigations. Bearing heavily on this ability is the ratio of fine roots to coarse roots. It takes a minimum amount of fine rootage to support the canopy under high water demand. If the container is full of large roots, there may not be room for a sufficient volume of the fine roots that do all the water/nutrient delivery work and the coarse roots, too. You can grow a very large plant in a very small container if the roots have been well managed and the lion's share of the rootage is fine. You can also grow very small plants, even seedlings, in very large containers if the soil is fast (free-draining and well-aerated) enough that the soil holds no, or very little perched water. I have just offered clear illustration that the oft repeated advice to "only pot up one size at a time", only applies when using heavy, water-retentive soils. Those using well-aerated soils are not bound by the same restrictions. ******************************************************** Shallow containers are the most difficult of all to grow in because if your soil holds 2-3" of perched water it will be 100% saturated after a thorough watering or rain shower. These pictures show cacti & succulents growing happily in less than 2" of soil (gritty mix) in clay saucers. They can sit outdoors in these shallow containers during a week of clouds & rain & not rot - no perched water .......... Al...See Morefungus gnats on sabal seedlings
Comments (3)The spray will probably be OK, but it will probably only kill on contact and 5 minutes later you have the same gnat problem. put a 1/2" of sand on top of the soil and that should stop the baby gnats from emerging from the soil....See MoreIs this damage root rot fungus?
Comments (2)The bushes have been in for many years -- at least 8. We had a couple of weeks of rain for awhile but they were looking really great then. We've not had rain for the past 10 days and this has happened during that period of time. Of course, I guess it can take time to produce the problem after the rain? None of them have been watered other than rain. All I could find online was about root rot fungus. They seem to be dying off so much faster than last year when they kinda held on and produced some flowers. I kept cleaning them up and pulling off all the dead leaves so they'd look okay, but they never really did "well" ya know....See Morerina_Ontario,Canada 5a
8 years agoDave
8 years agoAkeel Edible Vegtables
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8 years agoOhiofem 6a/5b Southwest Ohio
8 years agolast modified: 8 years agoewwmayo
8 years agoTamiya #1 (AU, SG, MY & ZZZzzzz...)
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8 years agoTamiya #1 (AU, SG, MY & ZZZzzzz...)
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8 years agoTamiya #1 (AU, SG, MY & ZZZzzzz...)
8 years agorina_Ontario,Canada 5a
8 years agoTamiya #1 (AU, SG, MY & ZZZzzzz...)
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8 years agolast modified: 8 years agoshawn b
8 years agoTamiya #1 (AU, SG, MY & ZZZzzzz...)
8 years agorina_Ontario,Canada 5a
8 years agoshawn b
8 years agolast modified: 8 years agorina_Ontario,Canada 5a
8 years agoshawn b
8 years agoPeter
8 years agoplantymomma
2 years ago
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Ohiofem 6a/5b Southwest Ohio